abstract: Integrins are a family of αβ heterodimeric transmembrane receptors. As an important class of adhesion receptors, integrins mediate cell adhesion, migration, and transformation through bidirectional signaling across the plasma membrane. Among the 24 different types of integrins, which are notorious for their capacity to recognize multiple ligands, the leukocyte integrin αMβ2 (Mac-1) is the most promiscuous member. In contrast to other integrins, Mac1 is unique with respect to its preference for cationic ligands. In this thesis, a new Mac-1 cationic ligand named pleiotrophin (PTN) is uncovered. PTN is an important cytokine and growth factor. Its activities in mitogenesis and angiogenesis have been extensively researched, but its function on immune cells was not widely explored. In this research, the cell biology and biochemical evidences show that PTN can regulate various Mac-1-expressing cells functions through the activation of the extracellular signal regulated kinases. Direct interactions between PTN and the αM I-domain, the major ligand-binding domain of Mac-1, has been shown using biolayer interferometry analyses and confirmed by solution NMR spectroscopy. The binding epitopes and the binding mechanism of PTN and αM I-domain interaction were further revealed by peptide array analysis and microscale thermophoresis. The data suggested that PTN’s thrombospondin type-1 repeat (TSR) domains and αM I-domain metal-ion-dependent adhesion site (MIDAS) are the major binding sites. In addition, this interaction followed a novel metal-ion independent binding mechanism which has not been found in other integrins. After a series of characterizations of αM I-domain using both experimental and computational methods, it showed that activated αM I-domain is significantly more dynamic than inactive αM I-domain, and the dynamics seem to modulate the effect of Mg2+ on its interactions with cationic ligands. To further explore the PTN induced Mac-1 structure rearrangement, intact Mac-1 was studied by negative stain electron microscopy. The results showed that the Mac-1 exhibited a very heterogeneous conformation distribution in detergents. In contrast, the Mac-1 adopted predominantly the bent conformation in phospholipid nanodisc condition. This Mac-1 nanodisc model provides a new platform for studying intact Mac-1 activation mechanism in a more physiologically relevant manner in the future. / Dissertation/Thesis / Doctoral Dissertation Biochemistry 2020

Microbial cross-contamination remains an on-going challenge in the food sector despite implemented sanitation programs. Antimicrobial coatings with inherent self-sanitizing properties have been explored to enhance current cleaning practice and support food safety. Prior work has demonstrated successful incorporation of dual antimicrobial characters, cationic polymers and N-halamines, into one coating system. In addition to the rechargeable nature of N-halamines, the coating was reported to exhibit biocidal effects due to the inherently antimicrobial cationic moieties and the chlorinated N-halamines. However, while these polymer coatings were able to retain antimicrobial activity after repeated chlorination, signs of hydrolysis was observed for the N-halamine bonds, indicating potential issues for long-term usage. Herein, we introduced varied molecular weight cross-linkers in an adaption of the established fabrication method to evaluate cross-linker molecular weight (styrene maleic anhydride (SMA) of 6, 8, 120, 250 kDa) influence on surface properties of the coating. All antimicrobial polymer coatings exhibited similar FTIR spectra, with a prominent absorption band at ~1650 cm-1 suggesting successful cross-link of the polyethyleneimine and SMA. Surface concentration of primary amines ranged from 350-900 nmol/cm2, and N-halamines from 90-130 nmol/cm2. Surface energy decreased with increasing molecular weight of SMA, but were not statistically different from one another. In the end, optimal cross-linker molecular weight was determined based on antimicrobial performance, where the coated PPs with 6 kDa SMAs demonstrated enhanced biocidal effects against E. coli O157:H7 in its chlorinated form. Further, the antimicrobial coating demonstrated efficacy of ~3 to >5 log reductions of microbial load in its unchlorinated and chlorinated form against E. coli O157:H7, L. monocytogenes, and P. fluorescens. Storage studies support the stability of the chlorinated halamines, with full retention of chlorinated N-halamines over a 24 h study (representative of time between sanitation cycles). These results support the potential application of this antimicrobial polymer coating in food processing and handling operations, in support of reducing cross-contamination of spoilage and pathogenic microorganisms.

Forward Osmosis (FO) is an emerging technology which has potential to operate with minimum energy input. High performance of FO systems depend on the availability of a suitable Draw Solution. Different types of Draw Solutions have been proposed, however; choosing a suitable one is still a developing area within the FO field. There is an urgent need to explore new materials in order to develop an efficient FO system. The current study aims at investigating the performance of three Draw Solutions namely, L-Alanine, DADMAC and PolyDADMAC as osmotic agents for FO. These organic cationic solutions can be used as extraction agents of water from poorer quality organic solutes such as fumaric acid solution produced in a continuous flow microbial fermentation process. The performance of the three Draw Solutions was evaluated by measuring the water flux and reverse solute diffusion at different concentrations. The viability of reconcentration of the diluted Draw Solutions was also investigated using Nanofiltration system. The performance and the efficiency of the Draw Solutions were studied via two separated bench scale systems of FO and Nanofiltration. Both Cellulose Triacetate (CTA) and Thin Film Composite (TFC) aquaporin protein FO membranes were employed under different orientations in FO set up operated for 24 hours or longer. In this study, NF90 membrane was used for reconcentration the Draw Solutions. A series of experiments were conducted to obtain the best water flux and reverse solute diffusion under various influencing operating conditions. The experiments were designed to achieve three objectives, i.e. (i) optimum operating conditions for FO system, (ii) optimum operating conditions for the reconcentration system, and (iii) implementation of the optimum operating conditions of the FO system for water recovery from a fumaric acid solution produced by a simulated industrial fermentation process. In the initial stage, L-Alanine Draw Solution demonstrated that it was the most viable agent for FO. It was established that L-Alanine Solution at 0.085 g/mL concentration achieved the highest initial water flux and the lowest reverse solute diffusion through both CTA and TFC aquaporin protein FO membranes. In the second stage, a Nanofiltration system was proven to be effective in the reconcentration of the diluted L-Alanine Draw Solution. The average rejection of L-Alanine ions achieved by NF90 membrane was 96.00%. Drawing on the previous results, the third stage was used to investigate the viability of the FO system in water recovery from fumaric acid solution produced by continuous microbial fermentation process using L-Alanine as a Draw Solution. The reduction of water content of the fumaric acid solution made it to concentrate by 26.00% and 19.80% in 32_ and 17_, respectively. Consequently, FO technology is an effective way to concentrate a fumaric acid solution produced by continuous microbial fermentation process. Based on the results, it is recommended that LAlanine should be proposed in the FO process according to its reliability and effectiveness as a viable draw agent. TFC aquaporin protein membrane is also recommended to be used in recover the water from fumaric acid solution produced by fermentation processes. Further studies should be done to investigate the viability of FO in water recovery from advanced application such as downstream bioprocessing. / Dissertation (MEng)--University of Pretoria, 2017. / Chemical Engineering / MEng / Unrestricted

The adsorption of cationic polyacrylamide (C-PAM) and silicananoparticles onto a model surface of silicon oxide wascompared with the adsorption of C-PAM to fibres and theirinfluence on flocculation of a fibre suspension. An increase inionic strength affects the polyelectrolyte adsorption indifferent ways for these two systems. With the silica surface,an increase in the ionic strength leads to a continuousincrease in the adsorption. However, on a cellulose fibre, theadsorption increases at low ionic strength (1 to 10 mM NaCl)and then decreases at higher ionic strength (10 to 100 mMNaCl). It was shown that the adsorption of nanoparticles ontopolyelectrolyte-covered surfaces has a great effect on both theadsorbed amount and the thickness of the adsorbed layer. Theresults showed that electrostatic interactions were thedominating force for the interaction between both the fibresand the polyelectrolytes, and between the polyelectrolytes andthe silica particles. Furthermore, at higher NaClconcentrations, a significant non-ionic interaction between thesilicon oxide surface/particles and the C-PAM was observed. The adsorption rate of C-PAM onto fibres was rapid andquantitative adsorption was detected in the time range between1 and 8 s at polyelectrolyte addition levels below 0.4 mg/g.Conversely, an increase in the amount of added polymer leads toan increased polymer adsorption up to a quasi-static saturationlevel. However, after a few seconds this quasi-staticsaturation level was significantly lower than the level reachedat electrostatic“equilibrium”. The adsorbed amountof charges at full surface coverage after 1 to 8 s contact timecorresponded to only 2 % of the total fibre charge, whereasafter 30 minutes it corresponded to 15 % of the total fibrecharge. This shows that a full surface coverage at shortcontact times is not controlled by surface charge. Based onthese results, it is suggested that a combination of anon-equilibrium charge barrier against adsorption and ageometric restriction can explain the difference between theadsorption during 1 to 8 s and the adsorption after 30 minutes.With increasing time, the cationic groups are neutralised bythe charges on the fibre as the polyelectrolyte reconforms to aflat conformation on the surface. The addition of a high concentration of C-PAM to a fibresuspension resulted in dispersion rather than flocculation.This behaviour is most likely due to an electrostericstabilisation of the fibres when the polyelectrolyte isadsorbed. Flocculation of the fibre suspension occurred at lowadditions of C-PAM. A maximum in flocculation was found ataround 50 % surface coverage and dispersion occurred above 100% surface coverage. It was also shown that for a given level ofadsorbed polymer, a difference in adsorption time between 1 and2 seconds influenced the flocculation behaviour. An optimum inflocculation at 50 % surface coverage in combination with theimportance of polymer reconformation time at these shortcontact times showed that the C-PAM induced fibre flocculationagrees with La Mer and Healy’s description of bridgingflocculation. A greater degree of flocculation was observed with theaddition of silica nanoparticles to the fibre suspension thanin the single polyelectrolyte system. Flocculation increased asa function of the concentration of added nanoparticles until0.5 mg/g. At higher additions the flocculation decreased againand this behaviour is in agreement with an extended model formicroparticle-induced flocculation. An increase in flocculationwas especially pronounced for the more extended silica-2particles. This effect is attributed to the more extendedpolyelectrolyte layer, since the adsorbed amount wasessentially the same for both silica particles. Finally it was found that fines from the wood fibres had asignificant effect on the flocculation. When fines were added,a greater degree of flocculation was detected. Furthermore, itwas also more difficult to redisperse the fibres with polymerin the presence of fines. <b>Keywords:</b>Adsorption, bridging, cationic polymers,cellulose fibres, electrosteric stabilisation flocculation,ionic strength, nanoparticle, polyelectrolyte, reconformation,retention aids and silica / NR 20140805

In the quest for a feedstock for the production of biofuels, microalgae are showing potential. High photosynthetic efficiency, combined with high lipid content and low fresh water requirement, has contributed to the 'biofuels feedstock' status of microalgae. In some communities, microalgae have also been cultivated in wastewater in facultative lagoons to remove phosphorus and nitrogen through the growth of microalgae. With such systems in place, complete biological wastewater treatment can be achieved and the harvested microalgae could provide feedstock for biodiesel and various other bioproducts. Due to small cell size, low culture concentrations, and the electrostatic repulsive forces that keep the cells in suspension, harvesting microalgae entails high energy inputs and associated high costs. Of the several harvesting methods tested, chemical precipitation has been shown to be the only method to harvest microalgae on a large scale. Although effective in wastewater treatment, the use of inorganic metal coagulants for microalgae harvesting leads to high dosage requirements, excess volume of sludge, and high costs, and due to the presence of associated metal hydroxide, the harvested biomass is unsuitable as feedstock for bioproducts. The drawbacks of inorganic coagulants for microalgae harvesting can be overcome by using cationic starch. Corn and potato starch were cationized using 3-methacryloyl amino propyl trimethyl ammonium chloride and biogenic amines. Flocculation efficiencies of the cationic starches were tested in a jar test apparatus using single strain microalga, Scenedesmus obliquus, and mixed culture wastewater from the Logan City, Utah lagoons. Cationic starches showed better or comparable removal of total suspended solids compared to aluminum sulfate. Total phosphorus removal efficiencies for cationic starches were lower compared to aluminum sulfate. Effect of cationic starch harvested and alum harvested S. obliquus on biodiesel, acetone, butanol, ethanol production, and Escherichia coli growth was also studied. Results suggested significantly higher yields of bioproducts when cationic starch was used to harvest microalgae and the biomass was used as feedstock. Cationic starches are an organic, sustainable, and renewable form of coagulant/flocculant. The use of cationic starch for harvesting microalgae eliminates the need for metal salts while enhancing the production of algae-based bioproducts. Cationic starch along with advanced technologies in the processing of microalgae is the way forward in the realization of the “microalgae to biofuels” initiative.

No description available.

Carbohydrates are central components of biological systems, with roles ranging from metabolism to immune signaling, and are utilized as antibiotics, anti-coagulants, and biomaterials. Carbohydrate polymers with ionic functionality, such as alginic acid and chitosan, are used in hydrogels, tissue engineering, drug delivery, and as nucleic acid vectors. The clinical translation of polysaccharide biomaterials is hindered by the poor chemical definition, poor batch-to-batch consistency, and demanding purification process of naturally-obtained material. Additionally, there are few synthetic methods yielding enantiopure, water-soluble carbohydrate polymers with high molecular weight. To address the need for translatable carbohydrate biomaterials, our group recently introduced bioinspired Poly-Amido-Saccharides (PASs) as enantiopure, water-soluble, and well- defined carbohydrate polymers. These previously reported PAS polymers, however, mimic polysaccharides with primarily metabolic roles due to the lack of charged functional groups important for biomaterial applications. In this thesis, I describe the synthetic methodology of a regioselectively amine-functionalized β-lactam carbohydrate monomer, the subsequent synthesis of enantiopure, water-soluble amine-functional PASs (AmPAS), an evaluation of AmPAS biocompatibility and mucoadhesivity for pharmaceutical formulations, and the use of AmPAS for biocompatible nanoparticulate delivery of nucleic acids. Protecting group choices and regioselective modification are key to the synthesis of the AmPAS monomer via [2+2] cycloaddition with electron-deficient isocyanates. The results of a combined experimental and theoretical study indicate that bulky protecting groups of the 6’-OH enforce a 5H4 glycal conformation and favorable overlap of ring σC-O* with the glycal allyloxocarbenium system that enhances negative hyperconjugation effects due to electron withdrawing protecting groups. These data inform AmPAS monomer synthesis, where bulky, electron-withdrawing groups are required for regioselective glycal functionalization and intermediate protecting group stability is necessary to obtain cationic, water-soluble AmPAS. These polymers exhibit minimal cytotoxicity and immunogenicity, and, through single molecule force spectroscopy and ex vivo methods, significant mucoadhesivity important for pharmaceutical application. AmPAS are obtained with tunable molecular weight distributions to allow for nanoscale size- and charge-matched supramolecular assemblies with single stranded RNA and DNA oligonucleotides. These nanoparticles are stable in high serum conditions, exhibit high cell uptake, and are shown to successfully deliver anti-miR-21 oligonucleotides to mediate miR-21 knockdown in vitro. These promising results motivate the future application of AmPAS in small molecule and antisense oligonucleotide delivery formulations. / 2022-01-28T00:00:00Z

<p> Cationic polyelectrolytes have attracted growing attention in the field of non-viral oligonucleotides (ONs) deliveries because of their ability to bind ONs by electrostatic interactions for efficient cellular uptake. However the formation of electrostatic polymer/ONs complexes and their biological effects are still poorly understood. The relationships between polymer structure and complexation performance have not been well established. The objectives of this research are to synthesize and characterize well-defined and well-controlled cationic polyelectrolytes and to evaluate the effects of polyelectrolyte chain properties on ONs complexation. Poly(2-(dimethylamino) ethyl methacrylate) (polyDMAEMA) and its derivatives are used as the polymer candidate. A fluorescein-labeled oligonucleotide, 5 '-FGCGGAGCGTGGCAGG-3' (F: fluorescein), is used as the oligonucleotide candidate.</p> <p> Low-molecular-weight cationic polyDMAEMA samples having narrow molecular weight distribution were synthesized by living anionic polymerization (LAP) and atom transfer radical polymerization (ATRP) methods. Fully charged polyDMAEMA quats were prepared by sequential quaternization of polyDMAEMA samples, as well as by direct ATRP of the quaternized DMAEMA monomer. An aqueous GPC calibration method was first developed for the characterization of these cationic polyelectrolytes. It was found that the type of counter-ion has little effect on the hydrodynamic volume of polyDMAEMA quat. Therefore the dimethyl sulfate salt of polyDMAEMA provided a reliable calibration standard for other types of quaternized DMAEMA homopolymers.</p> <p> Cationic block copolymers of polyDMAEMA with 2-hydroxyethyl methacrylate (HEMA) and polyethylene glycol (PEG) were also prepared by ATRP. It was found that the order of monomer addition, solvent type, temperature, and molecular weight of macroinitiator have significant effects on the living feature of the polymerization. Well-controlled block copolymers were obtained when polyHEMA was used as the macro initiator.</p> <p> The complexation capability of the prepared polyelectrolytes with oligonucleotides (15 mer) was evaluated by a fluorescence technique. It was found that the complexation performance depends on polymer molecular weight, charge density, and counter-ion type, as well as polymer concentration and block composition. The polymer sample that has double molecular weight of the ONs gave the optimal complexation performance.</p> / Thesis / Master of Applied Science (MASc)

<p> In part I of this dissertation, several cationic polyacrylamides were tested under different conditions for their ability to improve the retention of fines in papermaking. A dynamic drainage jar was used to simulate the turbulence encountered in the papermaking process. Several factors, including temperature, the amount and intensity of turbulence, the additive concentration and the presence of impurities were found to affect fines retention with polymers present. A polymer made by Nalco Chemicals proved to be superior to a commonly used polymer, Percol 292 for a standard fine paper pulp. It was thought that further retention improvements might be possible by tailoring the charge density and molecular weight of polyacylamide retention aides for the specific papermaking system they are intended for. Novel approaches to retention such as those employing combinations of an anionic polymer, a cationic polymer and zirconium oxychloride were thought to show promise as well.</p> <p> In part II of this dissertation several broad polyacrylamide molecular weight standards were prepared by inverse suspension and solution processes on pilot plant equipment at the McMaster Institute for Polymer Production Technology. They were characterized by laser light scattering and viscometry at McMaster, and externally by other methods. Although the polyacrylamides prepared compare favourably to currently available commercial standards when both are analysed by SEC, further analysis must be done to be certain of the molecular weight averages.</p> <p> A relationship is presented to provide for simpler and more accurate light scattering analysis in the future. This relationship relating Mw to the second Virial coefficient may be used to eliminate some uncertainty in the often scattered plots encountered when calculating molecular weights for polyacrylamides analysed by light scattering.</p> / Thesis / Master of Engineering (MEngr)

Since the surfaces of cantaloupes are highly rough or irregular, Salmonella enteric and other bacteria can easily attach to these surfaces and are difficult to remove. Cetylpyridinium chloride (CPC) is the active ingredient of some antiseptic oral mouth rinses and has a broad antimicrobial spectrum with a rapid bactericidal effect on Gram-positive pathogens. Delmopinol hydrochloride (delmopinol) is a cationic surfactant that is effective for treating and preventing gingivitis and periodontitis. The application of delmopinol or CPC to cantaloupe surfaces may be an alternative post harvest technique to reduce the frequency and level of Salmonella contamination. Cantaloupe (Athena and Hale's Best Jumbo (HBJ) cultivars) rind plugs were inoculated with a broth culture of Salmonella Michigan. After 15 min, plugs were sprayed with 10 ml of a 1% delmopinol solution, or a CPC solution (0.5 or 1.0%) or distilled water (Control), and held at 37 oC for 1 hr or 24 hr. For additional samples, the chemical treatments were applied 15 min before pathogen inoculation. Melon plugs were submerged in Butterfield's Phosphate Buffer, shaken, sonicated and solutions were enumerated on Tryptic Soy Agar. The texture quality and color of additional melon samples were evaluated after delmopinol or CPC spray treatments and storage at 4 oC. A 1.0% application of CPC reduced Salmonella levels up to 2.34 log CFU/ml (Athena) and 4.95 log CFU/ml (HBJ) in comparison to the control (p<0.01). A 1.0% delmopinol treatment reduced Salmonella levels as much as 3.1 log CFU/ml in comparison to the control (p<0.01) on both cultivars. In general, the log recovery of Salmonella on cantaloupes treated with delmopinol or CPC solutions, after 1 hr storage, was significantly lower (p<0.05) than the recovery from control cantaloupes, but Salmonella recovery was not significantly different after 24 hr. No significant differences were observed in the texture and color of melons treated with delmopinol or CPC after 14 days. A surface spray application of delmopinol hydrochloride or cetylpyridinium chloride could be an alternative antimicrobial post-harvest treatment that could make cantaloupes surfaces more susceptible to sanitizers or enhance physical removal of bacteria. / Ph. D.